Compressor Windings Check – DC Inverter Compressor
Use the following checks as a quick reference when assessing the windings of a DC inverter compressor.
Key principle: All three compressor windings should have an equal resistance value. For the compressors covered by this training reference, winding resistance is typically approximately 1–2 Ω at 20–25°C.
1. Compressor terminal identification
| Terminal | Reference | Lead colour shown |
|---|---|---|
| U | R(U) | Red |
| V | S(V) | White |
| W | T(W) | Black |
2. Winding resistance check
Measure the resistance between each pair of compressor terminals:
| Measurement | Expected result |
|---|---|
| U – V | Resistance should be approximately equal to the other two winding measurements. |
| V – W | Resistance should be approximately equal to the other two winding measurements. |
| U – W | Resistance should be approximately equal to the other two winding measurements. |
Example – AOTG18/22/24KMTC:
Compressor winding resistance shown in the training reference is 1.916 Ω at 20°C. The three U–V, V–W and U–W readings should be equal.
Compressor winding resistance shown in the training reference is 1.916 Ω at 20°C. The three U–V, V–W and U–W readings should be equal.
3. Insulation resistance check
The insulation resistance from any compressor winding to earth must be:
Greater than 1 MΩ
4. How to interpret the readings
| Check | Reference |
|---|---|
| U–V, V–W and U–W | All three winding resistance readings should be equal. |
| Typical winding resistance | Approximately 1–2 Ω at 20–25°C for the compressors covered by this reference. |
| Winding to earth | Insulation resistance must be greater than 1 MΩ. |
5. DC inverter compressor reference
- Rotary, twin rotary and scroll compressor types are commonly used in Fujitsu General products.
- Most compressors use 4-pole or 6-pole motors.
- Compressor speed can be calculated from operating frequency and motor pole count.
Hz ÷ (motor poles ÷ 2) = rps | rps × 60 = rpm
Electrical safety: Compressor terminal and insulation testing must only be undertaken by appropriately qualified service personnel using suitable test equipment and safe electrical work practices.